1. Field of the Invention
The present invention relates to film break detection systems in photographic film processors, and in particular, it relates to break detection systems for the detection of film breaks in a photographic film dryer of a photographic film processor.
2. Description of the Prior Art
In typical commercial photoprocessing operations, individual lengths of photographic film from many customers are spliced together to form a long continuous web of photographic film. The web is then photoprocessed in a photographic film processor to develop the photographic images recorded on the film. The photographic film typically has a "wet section" where the photographic film is transported through tanks containing developer, fix, and wash solutions to permanently affix the photographic images to the film base. The processor also typically includes a dryer section which dries the photographic film immediately after it leaves the wet section. The dryer normally includes a controlled humidity chamber in which the photographic film is dried. A heated gas medium, such as air, is circulated within the dryer to dry the photographic film as it is transported under tension through the dryer section.
This manner of film developing is for the most part a continuous process where residence time in the chemical solutions of the wet section and in the dryer have been calculated for both proper development and drying of the film and for highest possible speeds in order to maximize economic efficiencies. A break in the photographic film web while being transported through the photographic processor results in a loss of time and possible damage to the images contained on the photographic film. Thus, it is of great importance to know when a film break has occurred so that corrective action can be taken to save the film from damage to splice the film, and to resume processing.
A break in the dryer section is especially costly since extensive damage to the photographic film and loss in down time can occur. If the photographic film breaks within the dryer before the film is dry, the film can collect inside the dryer and stick to itself like flypaper. The images will either be ruined or lost as the film is pulled apart. This is particularly disasterous since the damage to the film cannot be reparied, and often the scenes photographed can never be duplicated. In addition, the down time incurred is a cost in terms of the photographic film that could have been processed while the dryer is being cleared of damaged film and the film is respliced.
Prior art photographic film processors have had film break indicators, but those break indicators of the prior art have been less than totally satisfactory since they typically have not indicated where the film break has occurred. Thus, the operator has had to search for the film break in the processor. During this search time, the wet photographic film can pile up in the dryer and be damaged. One such type of break indicator includes a magnet attached to a roller on the loading end of the machine, and a magnetic sensor positioned near the roller to sense the magnet as it passes with each revolution of the roller. As the photographic film is pulled off a loading reel, it engages and rotates the roller. If the magnet does not pass the magnetic sensor within a predetermined time, a film break is indicated by an alarm. This type of break indicator, however, does not tell the operator where in the entire processor the film has broken, only that a break has occurred.